You are incorrect. (see the last paragraph of the cite - the kid had one thing wrong, the US flag should have been on the right, or passenger, side)
Flying a flag outdoors will soil it, and tear it. Flying it from Fort McHenry did, in spades.
“Automobile and Motorcycle Flag Display Guidelines for Non-Military Vehicles
No other flag should be flown higher than the Flag of the United States of America. No other flag
should be noticeably larger than the Flag of the United States of America. The U.S. Flag is mounted on
its own right as the vehicle is moving forward, EXCEPT when it is mounted as follows …
A single U.S. Flag mounted on the roof of an automobile or a truck, or on the rear fender or
“bumper” of a motorcycle, CAN be mounted in the center of the vehicle OR it can be mounted
on the right side (passenger side) of the vehicle.
The U.S. Flag can be displayed in the center of a row of an odd number of flags (i.e. three flags,
five flags, seven flags, etc.) mounted across the roof of an automobile or truck or in a fendermount
or bumper-mount on the rear of a motorcycle. In this case, the U.S. Flag should be
higher than all other flags. “Higher” means that the uppermost red stripe of the flag should be
above the top of all other flags. This can generally be accomplished by using a U.S. Flag one
size larger than all of the other flags or by extending the length of the pole holding a U.S. Flag
that is the same size as all of the other flags.
The U.S. Flag displayed in the center of a row of multiple U.S. Flags mounted in a line across the
roof of an automobile or truck, or in a fender-mount or bumper-mount on the rear of a
motorcycle, CAN be higher than all of the other U.S. Flags (in the case of an odd number of
multiple U.S. Flags, i.e. three flags, five flags, seven flags, etc.) … OR … all of the U.S. Flags can
be the same height and size.
If a row of multiple U.S. Flags has an even number of flags (i.e. two flags, four flags, six flags,
etc.), ALL of the flags in the row should be the same height and size.
If U.S. Flags are flown from poles extending out of the “post holes” in the rear of, and on both
sides of, the bed of a pickup truck, both U.S. Flags should be the same size and height.”
http://www.newlondonmotorcycleclub.com/uploads/Flag_Guidelines.pdf
My point about flags on firetrucks - full size, no less - is they drag on the vehicle ITSELF. Never mind it is getting flooded with exhaust. Letting it touch anything or get blatantly dirty in any fashion is part of the code, regardless of flag situation.
The Code itself states for vehicles:
(b) The flag should not be draped over the hood, top, sides, or back of a vehicle or of a railroad train or a boat. When the flag is displayed on a motorcar, the staff shall be fixed firmly to the chassis or clamped to the right fender.*
*Note: this was changed in ‘76 apparently (my book from the ‘61 has the original). The original wording is “radiator cap”, not “right fender”. The cap was front and center.
To read this, it might be surmised that it is OK to drape the flag over the FRONT of the vehicle, as the only thing not mentioned (trunks, per se, did not exist then, so perhaps the writers did not think of saying “trunk lid”; I guess we can drape it there too). Chasses are very hard to access these days, so apparently that leaves right fender (new language). Which one might think means front OR back. Again, new-fangled only. In the old days, it was “rad cap”, which was only ever front and center.
I can see the confusion over this; but reading the rest of the code, I think it’s plain the intention. The flag is always to be in the front in other processional issues (what are positions on President’s car lately? I always saw SMALL flags - less easily desecrated - on the FRONT of the fenders), and in most groupings. I do not know why it would be different here. Likewise with the sections regarding soiling:
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The flag should *never touch anything* beneath it, such as the ground, the floor, water, or merchandise.
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The flag should never be fastened, displayed, used, or stored *in such a manner* as to permit it to be *easily torn, soiled, or damaged* in any way.